Data storage systems are used to store information provided by one or more host computer systems. Such data storage systems receive requests to write information to a plurality of data storage devices and requests to retrieve information from that plurality of data storage devices.
Point-in-time (“PIT”) data comprises data generated at a specified time. When portions of such point-in-time data are updated later, the original point-in-time data is first copied to target data storage before that original PIT data is updated. This procedure preserves the original PIT data. If the original PIT data is updated in a random order, then using prior art methods the original PIT data to be updated is written to the target storage in a similar random order.